The present invention pertains to a rod section commonly used in coupled multiples for the purpose of forming an underground hole and then installing a pipe or the like through the length of the hole. This is accomplished by digging operating and target trenches on opposed sides of the area to be spanned by an underground pipe. A pipe installer device is properly positioned in the operator trench and a first rod section is disposed in the device from the back end. The first pipe section is driven forwardly by appropriate power means of the installer until the trailing end thereof closely approaches the installer back end. A second rod section is coupled to the trailing end and the forward drive operation is continued. Rod sections are continually coupled to the preceding section until the leading end thereof emerges into the target trench. A front end cap provided on the leading tip end is then removed and an adapter is threaded thereon which is fixed to an end of a pipe to be installed through the length of the hole. The direction of drive is then reversed and the pipe is pulled backwardly into the length of the formed hole.
The above procedure is generally conventional, however, a problem exists, the couplers, on occasions, become crimped along one or both peripheral edges to the rod sections in a manner so as to render them unusable. The operating trench must be dug to a length sufficiently longer than the installer device, 6 feet longer, for example, to permit the coupled addition of rod lengths as the pushing operation progresses as above described. It is, therefore, impractical to manually dig a longer trench, often to substantial depths, to accommodate a plurality of permanently locked together rod lengths, consequently, they are discarded. The rod lengths are formed of a very hard expensive material such as steel to withstand the very substantial forces to which they are subjected.
Therefore, one of the principal objects of the present invention is to provide a reduced diameter screw threaded stud portion on each end of each rod section with an unthreaded shoulder portion connecting between the screw threaded stud and the main length of the section. The shoulder portion is of a diameter to slidably engage in an unthreaded lead-in portion of the coupler in a manner so as to prevent inward crimping of the unthreaded peripheral lead-in end portion under the very substantial radially directed forces to which they are often subjected during the hole forming operation.